Danny, As they say I've been "otherwise engaged" in recent weeks and have got rusty. I should have double checked before I posted. When I saw Ron's response I realised I was wrong and said so, but I didnâ€™t have time then to look any further.

Check this alternative elimination using that UR in a single AIC I believe I've found that reduces the puzzle to singles:

Considering the purpose of this thread I was trying to weave the UR inference into a killing AIC. Using GEM, all the eliminations are shown in one mark-up, but I can't string them together into a single AIC.

Danny, as your UR cells contain the only instances of 6 in row 3, it's clearly impossible. How kosher it is to use its possibility as premise is therefore questionable but I guess that wouldn't concern you. However, I take such instances to indicate that there should be more telling exclusion chains about.

Still using uniqueness, there's this chain to show that if r3c1 contains 5 a (14) deadly pattern would be created in the top tier:

David, I accept that a false premise may lead to multiple contradiction states. That's not the issue. The question still remains as to whether or not a Mike Barker UR pattern exists that would explain r2c9=1 leading to a DP contradiction using the bivalue cells r1c3 and r3c8?

Danny in Mikes figure I believe it's implied that there is a compund strong link between the b's involved as shown in the chain I give below, otherwise it would be possible to solve the cells as shown on the right.

Danny, I'm reasonably sure that Mike Barker did not define such a pattern. One has to draw the line somewhere, and I think that line is ... "include one ALS but not two."

David P Bird wrote:Danny in Mikes figure I believe it's implied that there is a compund strong link between the b's involved ...

No implicit strong links are required. There already is a set of seven explicit strong inferences: (1) the four cells of the UR, (2) the two conjugate links on 'a' as shown, and (3) the (a)(b)y cell that combines with the 'aby' cell of the UR to comprise an ALS.